Apparatus for guiding a fabric in a paper machine

Abstract: The invention concerns an apparatus for guiding the transverse position of a fabric in a paper machine, such as a drying wire (10), a press felt (20), or of an equivalent fabric. The guide apparatus comprises an alignment roll (60) for the fabric (10,20), the axial alignment of said alignment roll being regulated by means of the guide apparatus. In the guide apparatus, a sledge (64) is fitted in connection with one or both of the bearing supports (63) of the alignment roll (60), the position of said sledge in relation to the frame part (62) of the apparatus being regulated by means of an actuator motor (61). The sledge (64) of the guide apparatus is fitted on linear guides (72,74) in the frame part (62) of the apparatus, being guided by said guides. The apparatus comprises a self-holding power transmission arrangement (65,70), which is operated by the actuator motor (61) of the apparatus.

Description: The invention concerns an apparatus for guiding the transverse position of a fabric in a paper machine, according to the preamble of claim 1, which is based on US-A-2 484 473. The prior-art wire guide apparatuses that are commonly used comprise a pneumatic bellows device, which is fitted in connection with a bearing support of the alignment roll so that the axial alignment of the alignment roll can be altered, whereby the transverse position of the fabric can be regulated. In this respect, regarding the prior art related to the present invention, reference is made to the applicant's FI Patent No. 77,434 (equivalent to US Patent 4,932,578). It is a drawback of the prior-art bellows devices and equivalent that the height of the apparatus is quite large, as well as that it is difficult to make the apparatus rigid enough, which results in problems of vibration. It is a further drawback that, for example, in the event of failure in the supply of electricity or of other disturbance, the pressure is lost in the bellows, in which case the apparatus is usually shifted to one of its extreme positions, as a result of which the fabric guided by the apparatus is guided to the side and is, as a rule, destroyed completely. It is also a drawback of the prior-art apparatuses for guiding a drying wire that the pneumatic bellows of the actuator have poor resistance to the temperatures present in the dryer section. It is a further drawback in the prior-art apparatuses that the position of their location is usually limited, because the guides of the displaceable sledge of the guiding apparatus, to which sledge the bearing support of the alignment roll is attached, can be loaded in certain directions only. It may also be considered a drawback in the prior-art apparatuses that there is a considerable distance between the guides of said sledge and the area of action of the bellows devices, which produces a torsion in the guides of the sledge, with resulting detrimentally high friction forces, which make precise adjustment of the position more difficult. The object of the present invention is to avoid the drawbacks that came out above and to provide a novel guiding apparatus with a more rigid construction, so that the problems of vibration can be largely avoided. It is a further object of the invention to provide an apparatus whose construction is self-holding, so that, for example, in the event of failure in the supply of electricity or some other disturbance, it is locked in its latest position, in which case the fabric guided by the apparatus is usually not damaged. Thus, the means for manual control can be omitted entirely if necessary. It is a further object of the invention to provide a guiding apparatus by whose means a precise regulation of the position of the alignment roll can be achieved with low friction, by means of which regulation even very little adjustments can be carried out without hysteresis in the position of the alignment roll and in the transverse position of the fabric that runs over said roll. It is a further object of the invention to provide a guiding apparatus in which there is no substantial distance between the moving sledge and the point of action of the force that displaces said sledge, in which case the torsional moments, the resulting friction forces and the hysteresis are lowered. In view of achieving the objectives stated above and those that will come out later, the invention is characterized by the features of the characterizing part of claim 1. It is an important advantage of the invention that the guiding apparatus is arranged self-holding, so that, in the event of failure, it is locked in the latest running position, in which case the fabric guided by it cannot drift to the side to be damaged. According to the invention, a play-free guiding apparatus of low friction is provided, by whose means the alignment of the alignment roll can be regulated very precisely without hysteresis. Owing to its linear guides and to the mutual fitting between said guides and the power transmission means, the guiding apparatus in accordance with the invention can be made rigid and with very little play, so that the problems of vibration can be avoided. In a preferred embodiment of the invention, the point of action of the force that displaces the sledge and the plane of support of the linear guides are placed substantially in the same plane, in which case the torsional moments and the resulting friction forces are lowered, and so is also the height of the apparatus. It is a further substantial advantage of the invention that the apparatus in accordance with the invention can be placed, without changes in the construction, in any position whatsoever, even hanging downwards as suspended from its linear guides. The guiding apparatus in accordance with the invention can be made into a small-size and closed package which is protected from outside contaminations, such as splashes. In the following, the prior art most closely related to the invention, problems involved in the prior art, and some preferred embodiments of the invention will be described in more detail with reference to the figures in the accompanying drawing. Figure A shows a prior-art tensioning device for a drying wire in the dryer section of a paper machine. Figure B shows a prior-art upper-felt tensioning device in the dryer section of a paper machine. Figure 1 shows an apparatus in accordance with the present invention for tensioning of a drying wire in a dryer section, in a way corresponding to Fig. A. Figure 2 shows an apparatus in accordance with the present invention for tensioning of an upper felt in a dryer section, in a way corresponding to Fig. B. Figure 3 is a side view of a guiding apparatus in accordance with the invention. Figure 4 shows the same as Fig. 3, with the shields of the box removed. Figure 5 shows the same as Fig. 4, viewed from above. Figure 6 is a vertical sectional view along the line VI-VI in Fig. 5. Figure 7 is an end view of an apparatus as shown in the preceding illustrations. Figure 8 shows a linear guide applied in the invention as an illustration in the transverse direction of the guide rails. Fig. A is a schematic side view of a single-wire group in a multi-cylinder dryer of a paper machine, which comprises drying cylinders 11 placed in the upper row and reversing suction cylinders 12 placed in the lower row, the drying wire 10 being passed over said cylinders so that, on the upper cylinders 11, the paper web W to be dried is placed in direct contact against the heated outer mantles of the cylinders, and on the reversing suction cylinders 12 at the side of the outside curve. At the right side of Fig. A, the drying wire 10a of the next cylinder group, its guide roll 13a, and the drying cylinder 11a are shown. The drying wire 10 is conditioned by means of the devices 15. On the top of the frame part 130 of the dryer group, there is an auxiliary frame, which comprises vertical parts 28a and 28b as well as a horizontal part 29, the prior-art drying-wire 10 guiding device 100 being fitted on said horizontal part 29 of the auxiliary frame, and the axial alignment of the alignment roll 60 being controlled by means of the bellows 101 and 102 placed inside the U-shaped frame part 103 of said guiding device. The drying wire 10 is guided by the guide rolls 13 and tensioned by the tensioning roll 30 in the device 110. The prior-art tensioning device 110 as shown in Fig. A comprises a tensioning roll 30, which is mounted on a carriage 116. The carriage 116 is displaced on its wheels 117 and 118 on a beam 119 by means of cables 111 and 112, which run over reversing pulleys 113 and 114, of which pulleys the pulley 114 is driven by a motor 115. When the carriage 116 and the connected tensioning roll 30 are displaced by means of the motor 115 in the direction of the arrow B, the tension T of the loop of the drying wire 10 can be regulated. In the following, with reference to Fig. B, a prior-art guiding apparatus 100 for a press felt 20 of the press section in a paper machine and the environment of application of said apparatus will be described. Fig. B shows a compact press section of a paper machine, which press section comprises a suction roll 22a, a smooth-faced centre roll 21, and a press roll 22b. In connection with the centre roll 21, the second and the third nip N 2 and N 3 of the press section are formed. The first press nip (not shown) is formed underneath the suction roll 22a. Through the nip N 3 , the press felt 20 runs, which is guided by the guide rolls 23 and by the alignment roll 60 and tensioned by the tensioning roll 30. In connection with the frame part 24 of the paper machine, at the operating side of the machine, there are openable intermediate pieces 25, after whose opening the upper felt 20 can be replaced. The prior-art alignment device 100 for the control of the transverse position of the upper felt 20 is substantially similar to that described above in relation to Fig. A. Fig. 1 is a schematic illustration of a drying-wire 10 guiding apparatus in accordance with the present invention, which apparatus comprises a sledge 64, on which one of the bearing supports 63 of the alignment roll 60 is mounted. The sledge 64 is displaced in the direction of the arrow A on a guide 26 fitted on the frame part 29 by means of the power of a motor 61. In Figs. 1 and 2, a device for displacement of the roll 30 for tensioning of fabrics 10;20 is shown, which device is described in more detail in the Patent Application No. 930398, which was filed on the same day with the present application. The device for displacement of the tensioning roll 30 comprises sledges 40 attached to the bearing supports 32, which sledges are displaced along the linear guides 42,44, being driven by the shaft 36 and the rack 41. Fig. 2 shows a so-called splice-turning device 53 as fitted between the sledge 40 and the bearing support 32, by means of which device 53 the alignment of the press-felt 20 tensioning roll 30 can be altered. By means of the apparatus in accordance with the invention, the axial alignment of the alignment roll 60 is adjusted by shifting the position of the bearing support 63 of the alignment roll 60 in the directions of the arrow A, in relation to the middle position, in a range of about ± 60 mm. The opposite bearing support of the roll 60 has been arranged stationary, in a way in itself known, however, so that regulation of the other bearing support 63 in the direction of the arrow A is possible. As an alternative, it is possible to place a guiding apparatus in accordance with the invention in connection with each of the bearing supports 63 of the alignment roll 60, in which case the opposite sledges 64 may be operated either in the same direction or in opposite directions. The guide device comprises a motor 61, such as an electric motor, a pneumatic motor, or a hydraulic motor, said motor operating the shifting screw 65 by the intermediate of a bevel gear 67. The motor 61 and its bevel gear 67 are connected to the frame part 62 of the guiding apparatus by means of a flange joint 66a,66b. The frame part 62 is attached onto the top of the frame beam 29 of the dryer section in the way shown in Fig. 1, and onto the frame part 24 of the press section in the way shown in Fig. 2. Fig. 1 is a schematic illustration of the regulation system 80, by whose means the transverse position of the drying wire 10 is regulated. The system of regulation 80 comprises measurement detectors 81 and 82, by whose means the transverse position of one or both edges of the wire 10 is monitored. From said detectors 81,82, measurement signals m 1 and m 2 are received, which are passed to the system 80. From the system 80, a regulation signal s is received, by whose means the motor 61 of the guiding apparatus is controlled. The system 80 also includes a set value unit, by whose means the transverse position of the wire 10 or, in a corresponding way, of the press felt 20 shown in Fig. 2 or of any other, equivalent fabric in a paper machine can be regulated and kept in a position in accordance with the set value. The guiding apparatus, which is shown in more detail in Figs. 3 to 8, comprises a sledge 64, on whose support the bearing support 63 of one of the axle journals of the alignment roll 60 is attached. The shifting screw 65 is supported at both of its ends revolvingly by means of the bearings 71a and 71b, in the way shown in Fig. 6, in connection with the frame part 62. The shifting screw 65 has a self-holding square thread 65k, on which there is a shifting nut 70, which has a corresponding inner square thread 70k. Said shifting nut 70 is fixed in connection with the moving sledge 64 in the way shown in Fig. 6. At both sides of the sledge 64, in connection with the frame part 62, there are stops 68 provided with springs, which stops limit the range of movement (± 60 mm) of the sledge 64 resiliently. To the top side of the frame part 62, two guide rails 72 are attached, which are parallel to one another and extend over the entire length of the distance of movement of the sledge 64. Underneath the sledge 64, linear ball-bearing units 74 have been fixed by means of screws 75, one such unit 74 being fitted in each corner of the sledge 64. As comes out best from Figs. 6 and 7, the support planes of the guide rails 72 and of the linear ball-bearing units 74 are placed in the same plane K-K as the power transmission point of the shifting screw 65 and nut 70, for which reason no torsional moment is produced at the linear guides 72,74. Moreover, the construction is preferably symmetric in relation to the vertical central plane that passes through the central axis of the shifting screw 65, said plane being denoted with the reference T-T in Fig. 7, by means of which symmetry the detrimental torsional moments are also reduced. Differing from the above, the shifting screw in the guiding apparatus may also be a ball screw (not shown), which is not self-holding, or an equivalent screw, in which case the locking of the sledge 64 upon failure in its latest position is arranged by means of the drive gear 67 of the shifting screw 65 and/or by means of a brake motor. At the right side of Fig. 3, the movement detector 80 is shown, which is connected to the shifting screw 65. From the movement detector 80, a signal f is received, which is passed to the regulation system 80 shown in Fig. 1 to indicate the position of the sledge 64 in the apparatus. In the following, with reference to Fig. 8, a preferred embodiment of the linear bearing arrangement of the sledge 64 will be described. The pairs of guide rails 72 are fixed to the frame part 62 by means of screws 73. On the guide rails 72, linear ball bearings 74 move, which are fixed to the sledge 64 by means of screws 75. As comes out best from Figs. 4 and 5, there are two pairs of linear ball bearings 74 on the sledge 64. The linear ball bearings 74 are characterized by high loading capacity in all different directions transverse to the longitudinal direction of the guide rails 72, by adjustable small plays and by rigidity as well as by relatively low friction. The linear guides of the sledge 64 comprise said guide rails 72, onto which four axial rolling grooves 78 for the bearings have been made. On the guide rails 72, ball bearing units 74 move, in whose interior there are bearing balls 76, which perform a closed circulating movement in the loops 77a,77b,77c,77d, which numerous successive balls that are "in turn" are supported with their carrying portions in each of said rolling grooves 78. The rolling grooves 78 on the guide rail 72 are placed in pairs and symmetrically so that each carrying row of bearing balls 76 transfers the contact load between the guide rail 72 and the ball bearing unit 74 at an angle of about 45° when examined in the sectional plane of Fig. 8. Owing to the arrangement of linear guides 72,74 described above, the guiding apparatus can be placed in any position whatsoever. In this way, an equally high loading capacity is obtained in the four different directions, which permits the guiding apparatuses in accordance with the invention to be placed in all sorts of different positions without substantial alterations of construction. The linear guides 72,74 mentioned above are commercially available bearing components in themselves known.

Claims: Apparatus for guiding the transverse position of a fabric in a paper machine, such as a drying wire (10), a press felt (20), or of an equivalent fabric, comprising an alignment roll (60) for the fabric (10,20), the axial alignment of said alignment roll being regulated by means of the guide apparatus, and which guide apparatus comprises a sledge (64) or equivalent fitted in connection with one or both of the bearing supports (63) of the alignment roll (60), the position of said sledge or equivalent in relation to the frame part (62) of the apparatus being regulated by means of an actuator motor (61), and said sledge (64) or equivalent of the guide apparatus being fitted on and guided by linear guides (72,74) in the frame part (62) of the apparatus said linear guides (72,74) having been arranged so that they can be loaded in all directions transverse to the direction of movement (A), the apparatus further comprising a self-holding power transmission arrangement (65,70), which is operated by said actuator motor (61) and which comprises a shifting-screw-nut combination (65,70), whose shifting screw (65) is journalled (71a,71b) on the frame part (62) of the apparatus, and at which shifting screw, the nut (70) placed on the outer thread of said screw is connected with the sledge (64) of the guiding apparatus characterized in that the linear guides comprise at least two linear guide rails (72) and at least two linear ball-bearing units (74) placed in connection with each of said rails (72), and that the shifting screw (65,65k) and the shifting nut (70,70k) of the apparatus are placed substantially symmetrically between said linear guide rails (72) substantially in their support plane (K-K). Guiding apparatus as claimed in claim 1, characterized in that the shifting screw is a screw (65) which is provided with a self-holding square thread and on whose outer thread (65k) a shifting nut (70) is fitted, which is provided with a corresponding inner square thread (70k) and which is connected with said sledge (64). Guiding apparatus as claimed in any of the claims 1 and 2, characterized in that the shifting screw of the guiding apparatus is a ball screw, which is not self-holding, and that the locking of the sledge (64) of the guiding apparatus is arranged by means of the drive gear (67) of the shifting screw (65) and/or by means of a brake motor. Guiding apparatus as claimed in any of the claims 1 to 3, characterized in that, between the frame part (62) of the guiding device and both ends of the sledge (64) that is displaced in its connection, there are limiter devices (68), which are provided with a spring and by whose means the range of movement of the sledge (64) is limited. Guiding apparatus as claimed in any of the claims 1 to 4, characterized in that the guiding apparatus is substantially symmetric in relation to the central plane (T-T) perpendicular to the support plane (K-K) of the linear guide rails, which central plane (T-T) is further placed on the central axis of the shifting screw (65) (Fig. 7).

Inventors: AUTIO JUKKA, AUTIO, JUKKA
Applicants: VALMET CORP, VALMET CORPORATION
Application year: 1994
Main classification: D21F1
IPC codes: D21F1